GENERAL METHOD OF SAMPLE TREES. 49 



''ij i':> ''3 . • . = volumes of mean sample trees of successive 



classes, 



Hi, Un, 113 . . . = numbers of trees in successive classes, 



tlien 



t 1= I'l X tii; \ 2= i'2 X ii.2 . . . 

 and 



T^ = Ti + ^2 + Tg + • . • = '-1 X 111 + 1-2 X 11-2 + rg X //3 + . . . 



(2.) The sample trees in the several classes differ in basal 

 area somewliat from the mean basal areas. 



If the volumes of the approximate sample trees are r/, r^', 

 V3 . . . and the corresponding basal areas = s/, s.,', S3, 

 . . . . then 

 ,. _ r/ X si y _ 1-2 X S2 . J. _ vs' X S3 



\ 1 T X III , » 2 ^r X ^2 , ' 3 } X 113 . . . 



Si S2 S3 



■^^ SiXiii = 'S'l = total basal area of the first class, 



S2X112 = So — total basal area of the second class, etc., 

 the volume of the wood is : 



y ^ v/XSt _^ V 2^X S, _^ Va^X S3 _^ 



Sj Sg S3 



(3.) Several sample trees are measured in each class. In 

 that case — 



h' + Si" + Si'" + . . . ' " S2' + S2" + S2'" + • • • 



etc., and 



si + si" H- si'" + . . . sa' + S2" + S2'" + . . . 



//. Cl'iihhing together several Clauses, leading to t//e Jletlod of the 

 ArilJnnetkal mean Saiiipte 7Vee. 

 In order to shorten the method described above and to 



reduce the number of sample trees to be felled, several, or all, 



classes may be clubbed together into a group. 



Let 



111, n.,, 7/3 ... be the numbers of trees in the several classes 

 si, S2, S3 . . . ., basal areas ,, ,, ,, ,, 

 hi, ]i2, /'3 • . . ,, heights ,, ,, ,, ,, 



Ji,J2,h . • . ,, form factors ,, ,, ,, ,, 



F.M. E 



